The association between night eating and body mass depends on age

Abstract: Night eating syndrome (NES) is marked by substantial evening or nocturnal food intake, insomnia, morning anorexia, and depressed mood. Originally, NES was described as an eating pattern among obese individuals. However, subsequent studies showed that NES also occurs among non-obese individuals, who appear to be younger than obese individuals with NES. Thus, it has been proposed that NES may lead to future weight gain, which may explain inconsistent findings about associations between NES and body mass. The current study investigated the relationships between age, body mass index (BMI), and night eating severity in a representative sample of German adults (n = 2317). It was found that age moderated the relationship between night eating severity and BMI. Specifically, night eating was positively associated with BMI in participants who were between 31 and 60 years old, but not in younger (< 31 years) or older (> 60 years) participants. Results indicate that age may indeed play an important role when examining the relationship between night eating and obesity. That is, weight gain may only occur after longer periods of engaging in night eating and, thus, no or only small relationships can be found in younger samples such as students. The positive association between night eating and BMI disappears in older individuals, which may be related to onset of illness associated with wasting.


Alex’s Notes: Night eating syndrome (NES) is an actual mental condition. Specifically, it is a form of Otherwise Specified Feeding and Eating Disorder where there is

  1. Consumption of at least 25% of daily food intake after the evening meal or at least two episodes of nocturnal eating per week,
  2. Awareness of those eating episodes, and
  3. At least three of the following: morning anorexia, a strong urge to eat between dinner and sleep or at night, insomnia, a belief that one must eat in order to initiate or return to sleep, or a worsening of mood in the evening

The current study sought to examine the relationships between NES severity, BMI, and age in German adults. The final sample population comprised a total of over 2300 people divided into several age groups: 21-30 years old, 31-40, 41-50, 51-60, 61-70, and older than 70 years. The average BMI was just over 25 kg/m2, but ranged from 14.65 to 50.41 kg/m2. The sample was evenly split between men and women. NES severity was assessed with the night eating questionnaire (NEQ).

Some associations

Sex and NEQ were not different between age groups, but BMI significantly increased with age with two interesting exceptions. The BMI’s were not different in persons between 41-60 years of age, or in persons 51 years of age or greater. A weak positive correlation was found between night eating severity and BMI across the entire sample, but this turned out to be moderated by age such that no relationship was found in younger (21-30 years) and older (>60 years) persons.


In terms of the young subjects, a likely scenario is simply that a more active and healthier lifestyle offsets the possible weight gain that night eating may lead to. Seeing how BMI increased with age from 21-40 years of age, the increasing amounts of psychological stress and reduced physical activity commonly seen in middle-aged persons suggest that night eating may precede weight gain if environmental factors permit.

For the older subjects, things are more intriguing, as the association between night eating and BMI disappeared despite the NEQ scores not changing with age but older persons having greater BMIs. On reason could be that night eating becomes offset by medical conditions or reduced appetite and food intake seen in the elderly. Alternatively, some older persons may simply lose their drive for night eating while their BMI remains stable. Regardless, all the data was based on self-report, the effects were small, and no causal inferences can be made.


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